Update config call for newer versions of ConfigParser

ConfigParser now uses `read_file` instead of `readfp`.

pocket_cli/config.py

@@ -13,7 +13,7 @@ class Configs:
         if not os.path.exists(path):
             return
 
-        self._config_parser.readfp(open(path))
+        self._config_parser.read_file(open(path))
 
     def get(self, name):
         try: